doc: draft release notes for v2.7

Start documenting the major changes to v2.7, in particular the UOS/SOS
term changes that impact the APIs and documentation, and the scenario name changes.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>

doc/release_notes/release_notes_2.7.rst

@@ -0,0 +1,149 @@
+.. _release_notes_2.7:
+
+ACRN v2.7 (DRAFT)
+#################
+
+We are pleased to announce the release of the Project ACRN hypervisor
+version 2.7.
+
+ACRN is a flexible, lightweight reference hypervisor that is built with
+real-time and safety-criticality in mind. It is optimized to streamline
+embedded development through an open-source platform. See the
+:ref:`introduction` introduction for more information.
+
+All project ACRN source code is maintained in the
+https://github.com/projectacrn/acrn-hypervisor repository and includes
+folders for the ACRN hypervisor, the ACRN device model, tools, and
+documentation. You can download this source code either as a zip or
+tar.gz file (see the `ACRN v2.7 GitHub release page
+<https://github.com/projectacrn/acrn-hypervisor/releases/tag/v2.7>`_) or
+use Git ``clone`` and ``checkout`` commands::
+
+   git clone https://github.com/projectacrn/acrn-hypervisor
+   cd acrn-hypervisor
+   git checkout v2.7
+
+The project's online technical documentation is also tagged to
+correspond with a specific release: generated v2.7 documents can be
+found at https://projectacrn.github.io/2.7/.  Documentation for the
+latest development branch is found at https://projectacrn.github.io/latest/.
+
+ACRN v2.7 requires Ubuntu 18.04.  Follow the instructions in the
+:ref:`gsg` to get started with ACRN.
+
+
+What's New in v2.7
+******************
+
+API and Documentation Updates for User VM and Service VM Terminology
+   More often than not, the terms "UOS" and "SOS" referred to the User VM and
+   Service VM components of an ACRN Hypervisor system and not to the VM's OS.
+   We've updated the hypervisor APIs and documentation to properly reflect these
+   names and removed uses of UOS and SOS.
+
+   In the code, uses of ``uos`` and ``sos`` in names were changed to ``user_vm``
+   and ``service_vm`` respectively.  When specifically referring to the OS of
+   these VMs, we now use ``user_vm_os`` and ``service_vm_os``. These changes
+   appear throughout the C files, as well as in the ``.xml`` configuration
+   files.
+
+   For example, here are examples of old and new names:
+
+   .. list-table::
+      :widths: 1 1
+      :header-rows: 1
+
+      * - Old Name
+        - New Name
+
+      * - ``#define SOS_SOCKET_PORT 0x2000``
+        - ``#define SERVICE_VM_SOCKET_PORT 0x2000``
+
+      * - ``pkt->uos_active``
+        - ``pkt->user_vm_active``
+
+      * - ``static uint16_t get_uos_count(void)``
+        - ``static uint16_t get_user_vm_count(void)``
+
+      * - ``static uint16_t get_phy_addr(uint8_t uos_id, uint16_t vaddr)``
+        - ``static uint16_t get_phy_addr(uint8_t user_vmid, uint16_t vaddr)``
+
+Update Scenario Names
+   The pre-defined scenario names were changed to be indicative of their
+   properties instead of an example use.  The "industry" scenario is now called
+   "shared", the "logical partitioning" scenario is now called "partitioned",
+   and the "hybrid" scenario name remains the same.
+
+   Here are the three configuration scenarios:
+
+   * **Shared**: The physical hardware resources can be shared among
+     post-launched User VMs. The Service VM (Device Model) provides device
+     emulation for the shared virtual devices.
+   * **Partitioned**: The physical resources are strictly dedicated to
+     individual pre-launched User VMs and there is no Service VM needed.
+   * **Hybrid**: The physical resource are dedicated to pre-launched User
+     VMs and the Service VM provides resource emulation and sharing for
+     post-launched User VMs, all in the same system configuration.
+
+Upgrading to v2.7 From Previous Releases
+****************************************
+
+We highly recommended that you follow these instructions to
+upgrade to v2.7 from previous ACRN releases.
+
+Generate New Board XML
+======================
+
+Board XML files, generated by ACRN board inspector, contain board information
+that is essential to build ACRN. Compared to previous versions, ACRN v2.7 adds
+the following hardware information to board XMLs to support new features and
+fixes.
+
+  - list features here
+
+The new board XML can be generated using the ACRN board inspector in the same
+way as ACRN v2.6. Refer to :ref:`acrn_config_workflow` for a complete list of
+steps to deploy and run the tool.
+
+Add New Configuration Options
+=============================
+
+In v2.7, the following elements are added to scenario XML files.
+
+- list elements here
+
+Document Updates
+****************
+
+We've updated references throughout the documentation to use "Service VM" and
+"User VM" instead of "SOS" and "UOS" respectively.
+
+We've also made edits throughout the documentation to improve clarity,
+formatting, and presentation:
+
+.. rst-class:: rst-columns2
+
+* :ref:`hv-device-passthrough`
+* :ref:`vt-d-hld`
+* :ref:`faq`
+* :ref:`gsg`
+* :ref:`overview_dev`
+* :ref:`hypervisor-make-options`
+* :ref:`acrn_configurator_tool`
+* :ref:`acrn_on_qemu`
+* :ref:`enable_ivshmem`
+* :ref:`enable-s5`
+* :ref:`using_grub`
+* :ref:`using_partition_mode_on_nuc`
+* :ref:`acrn-dm_parameters`
+* :ref:`acrntrace`
+
+Fixed Issues Details
+********************
+
+.. comment example item
+   - :acrn-issue:`5626` - [CFL][industry] Host Call Trace once detected
+
+Known Issues
+************
+